Calculate how many CMU concrete blocks, mortar bags, grout fill, rebar, and estimated cost you need for any concrete masonry unit wall project in the United States — instantly and free.
Enter your wall dimensions, block size, and project details to calculate blocks, mortar, grout, rebar, and estimated cost.
Most common US size — ASTM C90 standard
Total linear feet of wall to be built
Standard 8" block courses = 8" per course
Combined area of all doors & windows to subtract
Full grout required for many seismic & load-bearing walls
2025 avg: 4"=$1.50, 6"=$2.00, 8"=$2.50, 12"=$4.00
A Concrete Masonry Unit (CMU) wall — commonly called a concrete block wall or cinder block wall — is one of the most widely used construction systems in the United States for foundations, basements, retaining walls, commercial buildings, and structural partitions. Standard CMU blocks manufactured to ASTM C90 measure 8"×8"×16" nominal (actual 7⅝"×7⅝"×15⅝") with a 3/8" mortar joint, yielding 1.125 blocks per square foot of wall face. To calculate total blocks needed, multiply wall area (minus openings) by 1.125, then apply a 10% waste factor for standard straight walls.
Standard 8"×8"×16" CMU: 1.125 blocks per sq ft of wall face. Each course is 8" high (7⅝" block + 3/8" mortar). Each block spans 16" (15⅝" + 3/8" mortar). A standard 8 ft wall = 12 courses. A 20 ft long × 8 ft high wall = 160 sq ft = ~180 blocks with 10% waste.
The most widely used CMU in the United States for residential and commercial construction. Medium weight (33 lbs), 4,000 psi gross area strength, costs $2.00–$3.00 each at Home Depot, Lowe's, or masonry suppliers. Covers 0.888 sq ft of wall face per block.
Used for load-bearing walls, retaining walls, and below-grade foundations in commercial and industrial construction. Normal weight (approx. 50 lbs), costs $3.50–$5.00 each. Provides greater lateral strength and is typically fully grouted with #5 or #6 rebar per TMS 402.
Used for non-load-bearing interior partitions, veneer wythe in cavity walls, and landscaping applications. Lightweight (approx. 18 lbs), costs $1.25–$2.00 each. Rarely grouted — typically ungrouted and unreinforced for partition-only use in commercial buildings.
A complete CMU wall material takeoff requires calculating blocks, mortar, grout, and rebar separately. Each material has its own coverage rate and waste factor. The formulas below follow standard US masonry estimating practice as used by contractors, estimators, and general contractors nationwide.
CMU blocks must be ordered in full units. Partial blocks at corners, window jambs, door openings, and bond beam courses add up quickly — always add a minimum 10% waste factor for straight walls and 15–20% for walls with multiple corners or complex layouts. Returning unused full pallets is generally possible, but partial pallets are non-returnable at most US masonry suppliers.
The table below lists standard ASTM C90 concrete masonry unit sizes available from US suppliers, with coverage rates, approximate 2025 retail costs at Home Depot and regional masonry yards, and typical structural applications per TMS 402/602 Building Code Requirements for Masonry Structures.
| CMU Size (Nominal) | Actual Size | Blocks / Sq Ft | Approx. Weight | 2025 Unit Cost | Typical US Use |
|---|---|---|---|---|---|
| 4"×8"×16" | 3⅝"×7⅝"×15⅝" | 1.125 | 18–22 lbs | $1.25 – $2.00 | Partition / Veneer |
| 6"×8"×16" | 5⅝"×7⅝"×15⅝" | 1.125 | 24–28 lbs | $1.75 – $2.50 | Light Structural |
| 8"×8"×16" ★ | 7⅝"×7⅝"×15⅝" | 1.125 | 30–38 lbs | $2.00 – $3.25 | Standard — Most Common |
| 10"×8"×16" | 9⅝"×7⅝"×15⅝" | 1.125 | 38–45 lbs | $2.75 – $4.00 | Medium Load-Bearing |
| 12"×8"×16" | 11⅝"×7⅝"×15⅝" | 1.125 | 45–55 lbs | $3.50 – $5.50 | Heavy / Retaining Wall |
| 8"×8"×8" (Half) | 7⅝"×7⅝"×7⅝" | 2.25 | 17–20 lbs | $1.50 – $2.50 | Corners / Closures |
A structurally sound CMU wall in the USA requires more than just blocks and mortar. Proper specification of grout, reinforcement, bond beams, and control joints is essential for code compliance under TMS 402/602, IBC 2021, and ACI 530. Understanding each component prevents costly rework and ensures your wall passes municipal inspection anywhere in the United States.
Standard structural CMU per ASTM C90 requires minimum 2,000 psi net area compressive strength and three density classes: Lightweight (<105 lb/ft³), Medium Weight (105–125), and Normal Weight (≥125 lb/ft³). Most US residential and commercial projects use medium weight 8" blocks.
Type S mortar (1 part Portland cement, ½ part lime, 4½ parts sand) is the standard for exterior, below-grade, and structural CMU walls in the USA. It provides 1,800 psi compressive strength. Type N mortar is used only for above-grade non-structural applications.
Grout fills hollow CMU cores around rebar to create a composite structural wall. Fine grout (max ⅜" aggregate) is used for cells up to 3"×3". Coarse grout (max ¾" aggregate) for larger cells. Most DOTs and structural specs require 2,000–3,000 psi grout per ASTM C476.
Vertical rebar (#4, #5, or #6) is placed in grouted cores to resist lateral loads, seismic forces, and soil pressure. Standard spacing is 32"–48" o.c. for most US residential walls. Seismic Design Categories D–F require closer spacing per IBC 2021 and ASCE 7-22.
Bond beam blocks (U-shaped top) receive horizontal rebar (#4 minimum) and grout at the top of the wall, above openings, and typically every 4 ft of height. They distribute lateral loads and tie the wall system together. Required at every floor line and roof bearing per TMS 402.
Control joints are vertical, unreinforced weakened planes spaced every 20–25 ft to accommodate shrinkage cracking. Per NCMA TEK notes, CMU walls without control joints in the correct locations will crack at random — control joints direct cracking to non-visible, sealable locations.
The table below provides quick-reference material quantities per 100 square feet of CMU wall face area for common US block sizes and fill configurations, based on standard ASTM C270 mortar and ASTM C476 grout specifications used across the United States.
| Block Size / Fill Type | Blocks per 100 Sq Ft | Mortar Bags (60 lb) / 100 Sq Ft | Grout — Full Fill (cu yd) | Grout — Partial (cu yd) | ASTM Standard |
|---|---|---|---|---|---|
| 4"×8"×16" — Ungrouted | 113 blocks | ~7 bags | N/A | N/A | ASTM C90 |
| 6"×8"×16" — Partial Grout | 113 blocks | ~8 bags | 0.60 yd³ | 0.25 yd³ | ASTM C90 |
| 8"×8"×16" — Partial Grout ★ | 113 blocks | ~9 bags | 1.12 yd³ | 0.40 yd³ | ASTM C90 |
| 8"×8"×16" — Full Grout | 113 blocks | ~9 bags | 1.12 yd³ | — | ASTM C90 |
| 10"×8"×16" — Full Grout | 113 blocks | ~10 bags | 1.38 yd³ | 0.55 yd³ | ASTM C90 |
| 12"×8"×16" — Full Grout | 113 blocks | ~11 bags | 1.65 yd³ | 0.65 yd³ | ASTM C90 |
US masonry suppliers sell CMU blocks by the pallet — typically 90 blocks per pallet for 8"×8"×16" units and 72 blocks per pallet for 12" units. Ordering full pallets saves $0.20–$0.50 per block vs. loose unit pricing and reduces delivery costs. Always confirm pallet quantities with your local supplier — quantities vary by manufacturer. Most suppliers offer free delivery for orders over 5–10 pallets.
Authoritative ASTM, TMS, and ACI standards for concrete masonry unit walls in the United States.
ASTM C90 is the primary US specification for load-bearing concrete masonry units, governing compressive strength (min. 2,000 psi net area), dimensional tolerances (±⅛"), and density classifications (lightweight, medium, normal weight) for all structural CMU applications.
View ASTM C90TMS 402/602 (Building Code Requirements and Specification for Masonry Structures) is the primary US masonry design code, adopted by the IBC and most state building codes. It governs reinforcement, grout, load-bearing design, and seismic requirements for all CMU wall systems.
View TMS 402/602The National Concrete Masonry Association (NCMA) publishes free TEK Notes — the industry's most comprehensive technical reference library for CMU design, detailing, estimating, and construction. Covers everything from mortar selection to seismic reinforcement for all 50 states.
View NCMA TEK Notes